which bind to DNA to form adducts. The formation of these adducts is believed to be the first step in the initiation of carcinogenesis. Carcinogen–DNA adducts also reflect an accumulated exposure over a longer period of time than urinary 1- OHP.
The urinary metabolites of benzene and PAHs have been used extensively for monitoring exposure to these pollutants because they are sensitive biomarkers of exposure. In this study, we have been able to observe sta- tistically significant differences in levels of both urinary metabolites in samples collected in rural school children and Bangkok city school children despite the relatively low levels of exposure. Additionally, t,t-muconic acid levels in urine samples collected in the afternoon, and 1- OHP levels in samples collected the following morning, did show a statistically significant correlation with per- sonal exposures to benzene and PAHs, respectively. This would seem to indicate that these are useful biomarkers of exposure, particularly since they are alsonon-invasive. However, only DNA adducts are generally accepted as being predictive of health effects, such as cancer (Vineis and Perera, 2000; Rundle et al., 2000).